Interlocking panels for large span roofs have been in use for some time. One of the most successful such panels is disclosed in U.S. Pat. No. 4,759,159 as having a pair of upstanding flanges at opposite longitudinal sides, a male rib supported by one flange and a female rib supported by the other flange, both the male and female ribs extending wholly to one side of their supporting flanges, the male rib engageable with the female rib of an adjacent panel to form an arcuate self supporting roof section for a building.
The female rib is defined as being of generally inverted U-shape form in transverse cross-section having a first leg comprising an extension of said supporting flange and a second leg spaced from said first leg, said second leg having a at its free end, an inwardly directed first deformation and there being provided a second deformation in the region of the junction between said first leg and said supporting flange.
The male rib is defined as being generally of an inverted U-shape form in transverse cross-section having a first leg comprising an extension of said supporting flange and a second leg spaced from said first leg and inclined outwardly away from said first leg, and there being an inwardly directed projection defining a recess in the region of the junction between said first leg and said supporting flange being complementary to said second deformation such that when interlocked said male rib is located within said female rib, said first legs of said male and female ribs are juxtaposed, said second leg of said male rib resiliently engages said second leg of said female rib rearward of said first deformation and said second deformation nests within said recess.
These known panels are formed in longitudinally curved sections and erected and joined to form self supporting roofs as shown in FIG. 1 of the drawings. However the nesting geometry of the inverted U-shapes is quite unforgiving of any deformation of the cross-section of the panel and the male rib tends to spring out of the female rib when the panel is flattened. The common solution to this has been to fasten the female rib to the male rib with screws which defeats the self interlocking of adjoining panels and adds to the cost of construction.